1. Field of the Invention
The present invention relates to a mobile communication system for supporting a multimedia broadcast/multicast service. More particularly, the present invention relates to an apparatus and a method for applying a direct tunnel feature in order to reduce a transmission delay of a mobile communication system for providing a Multimedia Broadcast/Multicast Service (MBMS).
2. Description of the Related Art
Today, with development of a communication technology, a service provided by a Code Division Multiple Access (CDMA) mobile communication system is evolving into multicasting multimedia communication for transmitting a large capacity data such as packet data, circuit data, etc. as well as a voice service. Therefore, to support the multicasting multimedia communication, a broadcast/multicast service for providing a service from one data source to a plurality of user terminals has been proposed. The broadcast/multicast service may be divided into a Cell Broadcast Service (CBS) which is a message dominant service, and a Multimedia Broadcast/Multicast Service (MBMS) for supporting a multimedia type such as real-time images and voices, still images, characters, etc.
Here, a mobile communication system for providing the MBMS is described below.
First, a Multicast/Broadcast-Service Center (MB-SC) which is a source providing an MBMS stream schedules a stream for an MBMS service and transfers the same to a transmission network. The transmission network denotes a network existing between the MB-SC and a Serving GPRS Support Node (SGSN), and transfers a stream for an MBMS service transferred from the MB-SC to the SGSN. Here, the SGSN may be configured using a Gateway GPRS Support Node (GGSN) and an external network, and assuming that a plurality of terminals that desire to receive an MBMS service at an arbitrary point exist, the SGSN that has received a stream for the MBMS service from the transmission network plays a role of controlling an MBMS related service of subscribers (terminals) that desire to receive the MBMS service. For example, the SGSN manages MBMS service billing related data of each subscriber and selectively transmits MBMS service related data to a specific Radio Network Controller (RNC). Accordingly, the Base Station Controller (BSC) transmits relevant service data to relevant terminals to allow the terminals to use the MBMS service.
That is, in the above-described MBMS service providing method, the GGSN transmits traffic to the BSC by way of the SGSN. The GGSN, SGSN, and BSC perform a session start process of transmitting/receiving a MBMS Session Start Request/Response message to/from a neighbor node, and then sequentially transfer data received from the GGSN to a node that has transmitted a previous MBMS session start response.
Accordingly, lots of nodes exist unnecessarily between terminals and the MB-SC in the mobile communication system while an MBMS service is provided, so that a transmission delay increases and a signal control is concentrated on the SSGN and so a load of the SSGN occurs.